The present invention relates to an electric circuit apparatus wherein semiconductor power devices of surface-mounting type are mounted on a circuit board by soldering.
Conventionally there exist an electric circuit apparatus wherein a plurality of circuit elements of surface-mounting type such as semiconductor power devices, electrolytic capacitors, resistors, etc. are surface-mounted on a circuit board by soldering.
In the conventional electric circuit apparatus, the circuit board is arranged in a vertical direction (in a direction of gravity) or in a horizontal direction. Therefore, when the semiconductor power device causes abnormal heat generation by a malfunction etc., the following problem occurs. That is, in case of the circuit board arranged in a vertical direction, the semiconductor power device drops when the solder melts by the abnormal heat generation of the semiconductor power device and is left in a casing of the electric circuit apparatus. Since the semiconductor power device of surface-mounting type has a planar back electrode formed on its back, if the semiconductor power device moves from its original position due to the influence of vibration etc., it is likely to cause problems such as short-circuiting of other circuit elements, and the like. On the other hand, in case of the circuit board arranged in a horizontal direction, the semiconductor power device does not drop when the solder melts by the abnormal heat generation of the semiconductor power device, but its abnormal heat generation continues and this may exert a bad influence on the other circuit elements.
It is the object of the present invention to provide an improved electric circuit apparatus wherein semiconductor power devices of surface-mounting type are mounted on a circuit board by soldering.
It is the object of the present invention to prevent continuous heat generation of the semiconductor power device and also prevent other circuit elements from being short-circuited in the event of the solder melting due to the abnormal heat generation of the semiconductor power device.
According to the present invention, the electric circuit apparatus is slantingly disposed so that the semiconductor power device falls out by its self-weight when the solder melts due to the heat generation of the semiconductor power device. The semiconductor power device is stopped by a stopper member and becomes in an electrically open state at the stopped position. Therefore, the continuous heat generation of the semiconductor power device is stopped.
The semiconductor power device is retained at the stopped position in consequence of the subsequent cooling of the solder. Therefore, the other circuit elements are prevented from being short-circuited.
The electric circuit apparatus preferably has a retention member for slantingly retaining the circuit board so that a semiconductor power device falls out by its self-weight. The retention member and the stopper member may be configured to be a single member.
The back electrode of the semiconductor power device may be partially fixed to the first electrode pad in consequence of the subsequent cooling of the solder so that the semiconductor power device is surely retained at the stopped position.
The other electrode terminal of the semiconductor power device may be soldered to the second electrode pad which is located at the opposite side of the stopper member with respect to the first electrode pad in an inclination direction of the circuit board so that the semiconductor power device surely becomes in an electrically open state when the semiconductor power device falls out.
In case where a plurality of semiconductor power devices are mounted on the circuit board, a plurality of stopper members may be provided to stop the falling of the respective semiconductor power devices. Alternatively a single stopper member may be provided to stop the falling of the respective semiconductor power devices. In the latter case, preferably, the other circuit elements may be positioned at a higher location than the plurality of semiconductor power devices.